a) Field of the Invention
The invention relates in general to a socket having an overheating destructive limiting element, and more particularly, to a socket having a limiting element made of an insulation material that positions a live wire terminal, a live wire conductive plate and/or a neutral wire terminal and a neutral conductive plate at a turn-on position. When an operating temperature gets too high, the limiting element becomes deformed and destructed to change the live wire terminal, the live wire conductive plate and/or the neutral wire terminal and the neutral conductive plate to a turn-off position.
b) Description of the Prior Art
To prevent a circuit from issues of current overload, short circuit and overheating, a fuse or an overload protector is usually provided at the circuit. When the temperature of the circuit gets too high or the current gets too large, the fuse affected by the high temperature becomes blown or a bi-metal shrapnel of the overload protector becomes disengaged, so as to cause the circuit become open circuit and turned off to ensure electricity safety.
Regarding the prior art of a fuse structure, for example, the Taiwan Patent No. 1371053 discloses “Temperature Fuse Connection Structure”, which mainly includes two terminals and a meltable metal. The two terminals are fixed and assembled at circuit wires, with two free ends of the two terminals respectively disposed with through openings. When not receiving an external force, the two free ends of the two terminals are kept at a distance in between. At least one of the two terminals is made of a flexible conductive material and is thus a flexible terminal. With the flexibility of the flexible element, an elastic force that separates the two free ends of the two terminals is formed. The meltable metal is penetrated through the openings of the two free ends. Two ends of the meltable metal are impinged by a riveting means to enlarge the two ends of the meltable metal. Further, the free ends of the two separated terminals are electrically connected, such that the free ends of the two terminals inwardly and closely come into contact while also being respectively separated outwards by the elastic force. In the event of current overload, circuit overheating or an excessively high ambient temperature, the meltable metal is heated to cause a rise in the temperature and becomes molten and broken. As such, the free ends of the two terminals become disconnected and the circuit then becomes a turn-off state.
However, due to reasons below, the above disclosure or the overload protector needs to be further improved.
First of all, in the “Temperature Fuse Connection Structure” disclosed by the Taiwan Patent No. 1371053, the meltable metal is a conductive material, and is shaped in a rivet form to electrically connect the free ends of two separate terminals. When the meltable metal is molten, it is possible that the molten and broken meltable metal be expelled from an original position by the elastic force of the two terminals, or remain stuck to the two terminals. If the molten meltable metal is expelled from the original position, with collisions against other objects or subsequent external forces, it is much likely that the molten meltable metal be moved back to between the two terminals or other positions that may connect the two terminals. As a result, the two terminals intended to be disconnected may again erroneously come in contact to form close circuit. If a part of the molten meltable metal remains stuck to the two terminals, the stuck molten meltable metal may also result in an erroneous contact between the two terminals to fail in a complete disconnection. Further, the expelled molten meltable metal also has a chance of coming into contact with other surrounding electronic elements to cause a short circuit. Therefore, such conventional solution is exposed to potential hazards and needs to be improved.
Secondly, in the “Temperature Fuse Connection Structure” disclosed by the Taiwan Patent No. 1371053, the meltable metal fixes the two terminals by a riveting means, which requires the two terminals to be provided with corresponding through openings. The presence of the two openings equivalently reduces the mutual contact area between the two terminals. When the current passes through the contact part of the two terminals, a higher operating temperature is caused because of the smaller contact area. More particularly, when the two terminals are selected from a thinner material with a preferred flexibility, e.g., when the two terminals are conductive copper plates having a thickness of 0.2 mm to 0.4 mm, the rise in temperature is very noticeable.
Thirdly, a conventional overload protector has a large volume. To apply the overload protector to a socket to obtain an auto power-off effect in the event of overheating, the socket also needs a larger volume. Especially for an extension socket, e.g., an extension socket having six socket units, if each of the socket units is provided with one overload protector, the volume of the extension socket will become huge as six socket units and six overload protectors are at the same time accommodated therein. Whether for storage, transportation or usage, such excessive volume inevitably causes complications and inconveniences.